Accelerated mineralization on photofunctionalized acid-etched titanium sustains distinguished mechanical properties

Intrinsic biomechanical properties of peri-implant bone play a crucial role in the short- and long-term stability of osseointegrated implants. We previously demonstrated the following: (1) the hardness and elastic modulus of peri-implant bone associated with acid-etched titanium surface were 3-fold and 2-fold greater than those of machined surface, respectively; (2) the hardness of acid-etched surface-associated bone were equivalent to those of cortical bone; and (3) the UV light-mediated photofunctionalization of titanium resulted in rapider and more complete establishment of osseointegration in vivo. However, the effects of UV light-induced accelerated mineralization on the biomechanical properties of peri-implant bone have never been addressed. Objectives: The objective of this study was to investigate the effects of photofunctionalization on the quantity and quality of cultured mineralized tissue. Methods: Commercially pure titanium disks were acid-etched and stored in a dark place for 4 weeks. Photofunctionalized surfaces were prepared from these disks by subjecting one-half of them to UV light pretreatment for 48 h. Rat bone marrow-derived osteoblastic cells were cultured on the disks with or without UV light pretreatment. At day 28, the nodule area, calcium deposition, and hardness of each mineralized culture were evaluated by image analysis, the o-cresolphthalein complexone method, and nano indentation test with loading rate of 1 mN/s, respectively. Results: Both the mineralized nodule area and total calcium deposition of mineralized cultures on the photofunctionalized surfaces were 1.7-fold greater than those of the control culture (p<0.01). In contrast, there was no significant difference in the calcium density of the mineralized tissues on both surfaces. Nanoindentation revealed that the hardness of the accelerated culture was equivalent to that of the control culture. Conclusion: The photofunctionalization of acid-etched titanium accelerated and enhanced osteoblastic mineralization sustaining distinguished mechanical properties in vitro. Thus, photofunctionalization leads to the enhancement of the anchorage of titanium implants.